'\" et
.TH SHM_UNLINK "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
shm_unlink
\(em remove a shared memory object
(\fBREALTIME\fP)
.SH SYNOPSIS
.LP
.nf
#include <sys/mman.h>
.P
int shm_unlink(const char *\fIname\fP);
.fi
.SH DESCRIPTION
The
\fIshm_unlink\fR()
function shall remove the name of the shared memory object named
by the string pointed to by
.IR name .
.P
If one or more references to the shared memory object exist when the
object is unlinked, the name shall be removed before
\fIshm_unlink\fR()
returns, but the removal of the memory object contents shall be postponed
until all open and map references to the shared memory object have been
removed.
.P
Even if the object continues to exist after the last
\fIshm_unlink\fR(),
reuse of the name shall subsequently cause
\fIshm_open\fR()
to behave as if no shared memory object of this name exists (that is,
\fIshm_open\fR()
will fail if O_CREAT is not set, or will create a new shared memory
object if O_CREAT is set).
.SH "RETURN VALUE"
Upon successful completion, a value of zero shall be returned.
Otherwise, a value of \-1 shall be returned and
.IR errno
set to indicate the error. If \-1 is returned, the named shared
memory object shall not be changed by this function call.
.SH ERRORS
The
\fIshm_unlink\fR()
function shall fail if:
.TP
.BR EACCES
Permission is denied to unlink the named shared memory object.
.TP
.BR ENOENT
The named shared memory object does not exist.
.P
The
\fIshm_unlink\fR()
function may fail if:
.TP
.BR ENAMETOOLONG
.br
The length of the
.IR name
argument exceeds
{_POSIX_PATH_MAX}
on systems that do not support the XSI option
or exceeds
{_XOPEN_PATH_MAX}
on XSI systems,
or has a pathname component that is longer than
{_POSIX_NAME_MAX}
on systems that do not support the XSI option
or longer than
{_XOPEN_NAME_MAX}
on XSI systems.
A call to
\fIshm_unlink\fR()
with a
.IR name
argument that contains the same shared memory object name as was
previously used in a successful
\fIshm_open\fR()
call shall not give an
.BR [ENAMETOOLONG] 
error.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Names of memory objects that were allocated with
\fIopen\fR()
are deleted with
\fIunlink\fR()
in the usual fashion. Names of memory objects that were allocated with
\fIshm_open\fR()
are deleted with
\fIshm_unlink\fR().
Note that the actual memory object is not destroyed until the
last close and unmap on it have occurred if it was already in use.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
A future version might require the
\fIshm_open\fR()
and
\fIshm_unlink\fR()
functions to have semantics similar to normal file system operations.
.SH "SEE ALSO"
.IR "\fIclose\fR\^(\|)",
.IR "\fImmap\fR\^(\|)",
.IR "\fImunmap\fR\^(\|)",
.IR "\fIshmat\fR\^(\|)",
.IR "\fIshmctl\fR\^(\|)",
.IR "\fIshmdt\fR\^(\|)",
.IR "\fIshm_open\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<sys_mman.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
